CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Can you provide a minimal example showing the pb?
With what you provide it is hard to guess what went wrong.

Sebastien.

On 6/6/19 10:47 PM, Rash wrote:
> Dear mailing list,
>
> why are there invalid indices when using surface mesh? I have 2275
> correct vertices in it. But somehow the mesh got 13637 vertices. Some of
> may be invalid.
>
> Lets have a look:
>
> Data in mesh -> vpoints_ -> data:
>
> [2] -0.532385 -2.32635 -0.1027
>
> Data in my file:
>
> Verts:
> [0] -0.532385 -2.32635 -0.1027
> Faces:
> [0] 2 4 13273
>
> The [0] 2 seems to refer to the internal mesh element address not to the
> second good vertex which mesh.point(vd) delivers.
>
> Strange why is the first vertex in my list the second in the mesh? Oh
> this is a pattern. There seem to be 13637 vertices in mesh, but only
> 2275 good ones. You may ask why. Or why there is no offset, which would
> correct for it when you write the data out. To be honest, it took me
> some time find this out. How do I get the correct indices?
>
> Here is some code.
>
>
>
> std::to_string(mesh.number_of_vertices()); //2275
>
>
> //2275 vertices, cool lets write them down to my debug file
>      for(Vertex_index vd : mesh.vertices())
>      {
>          const Point p(mesh.point(vd));
>          myfile << p.x() << " " << p.y() << " " << p.z() << std::endl;
>      }
>
>
> //cool now i go over all faces, save the vertex indices and have my nice
> mesh
>
>      for(auto it = faces.begin(); it != faces.end(); it++)
>      {
>          face_descriptor fd = *it;
>
>
>          HalfEdgeIndex edge = mesh.halfedge(fd);
>
>          Vertex_index vert1=source(edge, mesh);
>          Vertex_index vert2=source(next(edge, mesh), mesh);
>          Vertex_index vert3=source(next(next(edge, mesh), mesh), mesh);
>
>         //save them to tris
>
>      }
>
>         //lets write the triangles into a file, easy we have Vertex_indices,
> right? Oh no, of course not. THIS IS CGAL (image this with king leonidas
> voice)
>      for(size_t i = 0; i < tris.size(); i++)
>      {
>          myfile << tris[i] << std::endl; //and we got the wrong indices,
> suprise!
>      }